Hm. Actually, that raises an obscure point to the setting (at least the one I had in my head, circa 3.5):
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In adventure 12, the PCs come across a trillith-like spirit called Time, which guards the Aquiline Heart. It takes the form of a ghostly dragon, and in my head I always thought that the creature was basically a trillith created by the Flamebringer Dragon.
Just as Trilla got weird psychic powers after having infernal and celestial energy poured into her, so too could the primordial fire spirit have gotten powers after consuming the flesh of the ancient air spirit, the Stormchaser Eagle. If you read adventure 10 of the 3.5 version, you might have noted that
A) Silesh-el-Mavisha, the Tidereaver, will answer queries;
B) Thuuga-el-Shembul, the Worldshaper, will too; but
C) Jhial-el-Avilona, the Stormchaser is dead except for her heart; and
D) Khor-el-Jiese, the Flamebringer will not respond to the heroes’ entreaties.
I always imagined (but never bothered to put into the saga) that Jiese ate the heart, realized he was being tempted by too much power, and in a brief moment of morality conjured a guardian to defend the Heart. Then he fled -- not to the Underdark like Trilla, but to another plane. Perhaps the Elemental Plane of Fire/Elemental Chaos. Perhaps one of the Nine Hells/Astral Dominions.
Maybe kalashtar were primitive people who witnessed the dragon's flight from this world, who allied with or defeated nightmare being spawned by the primordial spirit before he gained control of his power.
Perhaps a kalashtar PC in adventure 3 might sense an inexplicable connection to something beyond the fire seal in the steam tunnels beneath Seaquen.
(If I had been more closely involved with adventure 11 originally, in order to provide an avenue for post-campaign epic-level play, I probably wouldn't have put a demon lord down there, but rather the lair of Khor-el-Jiese.)[/sblock]